Aiming at the problem of missed diagnosis and misdiagnosis caused by the system uncertainty in the application of analytic redundancy relation based fault diagnosis， this paper introduces the interval analysis into the traditional bond graph linear functional transformation technique（BG-LFT）， and proposes an interval redundancy relation based fault diagnosis method. Firstly， the unified modeling for parameter and measurement uncertainty based on BG-LFT are combined with the interval analysis method. Then， the bond graph model is extended to the uncertain bond graph model， and the analytical redundancy relations are transformed into the interval form. Finally， the diagnostic threshold is calculated by the interval mathematical calculation method. The method is applied to the parametric and sensor fault diagnosis of an electro-hydraulic actuator. The results show that compared with single BG-LFT， the proposed method can obtain the diagnosis basis of the electro-hydraulic actuator more effectively， and avoid the interference of system uncertainty to the diagnosis results.